Mixing leaded and lead-free BGAs (Ball Grid Arrays) into one PCBA (Printed Circuit Board) can be a challenging task for PCBA manufacturers. The primary reason is that leaded and lead-free BGA have different melting temperatures, and the reflow profile required for each type of BGA is different. Lead-free BGAs require higher reflow temperatures and longer soaking times to achieve proper solder wetting and formation, while leaded BGAs require lower temperatures and shorter soaking times.
If the reflow temperature and profile are not properly optimized, it can result in various issues such as solder joint cracking, insufficient solder wetting, and voids in the solder joint. These issues can lead to device failure and can compromise the reliability of the PCBA.
To avoid these issues, PCBA manufacturers may use separate reflow profiles for leaded and lead-free BGAs, which can be time-consuming and costly. Another option is to use a mixed-alloy solder paste that can accommodate both leaded and lead-free BGAs, although this can also be challenging as the optimal solder paste composition can vary depending on the specific BGA type and PCBA design.
Moreover, mixing leaded and lead-free BGAs may also result in issues with RoHS compliance. RoHS (Restriction of Hazardous Substances) is a regulation that restricts the use of certain hazardous substances in electrical and electronic equipment, including lead. PCBAs containing leaded BGAs may not be RoHS compliant, which can limit their use in certain applications.
Therefore, PCBA manufacturers should carefully evaluate the requirements and design of the PCBA before deciding to mix leaded and lead-free BGAs into one PCBA. They should also ensure that the reflow profile is properly optimized to achieve reliable solder joints, and that the PCBA is RoHS compliant if necessary.
